In old astrology, a planet was said to be in its exaltation when it was in that sign of the zodiac in which it was supposed to exercise its strongest influence. Thus the exaltation of Venus is in Pisces, and her dejection in Virgo.

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And thus, God wot, Mercry is desolate

In Pisces, wher Venus is exaltate.

Chaucer; Canterbury Tales, 6,285.

In chemistry, the refining or subtilising of bodies, or of their qualities, virtues, or strength.